Field of the Invention
The present invention relates to a gettering layer forming method for forming a gettering layer on a wafer, the gettering layer having a function of capturing impurities.
Description of the Related Art
There is an increasing chance of thinning a wafer by any method such as grinding before dividing the wafer into device chips, so as to reduce the thickness and weight of each device chip adapted to be incorporated into electronic equipment or the like. For example, the wafer can be thinned by rotating a tool (abrasive member) containing abrasive grains dispersed in a bond and pressing this tool against a work surface of the wafer to thereby grind the work surface.
In grinding the wafer as described above, minute marks (flaws) or strain may be produced on the work surface of the wafer. Such marks or strain has a gettering function of capturing impurities such as copper (Cu) having an adverse effect on the device chips. Accordingly, by leaving such marks or strain on the wafer, the fraction defective of the device chips due to the impurities can be reduced.
However, when the marks or strain is left on the wafer, the die strength of each device chip is apt to decrease. To cope with this problem, the marks or strain is frequently removed by any method such as polishing and etching after grinding the wafer. In this case, minimum required marks or strain is formed again on the wafer to thereby obtain a necessary gettering function (see Japanese Patent Laid-open Nos. 2014-63786, 2015-46550, and 2016-182669, for example).